This article is part of our special report The Scale Issue.
Illustrations: Optics Lab If you want to get a sense of the truly global scale of the electronics industry, look no further than your smartphone. The processor that powers it started as a humble rock, and by the time it found its way into your device, it had probably seen more of the world than you have. Along the way it was subjected to some of the most technologically sophisticated and closely guarded processes on the planet. Come along as we retrace that incredible 30,000-kilometer ride.
1. Quartz Your smartphone processor began its journey in the northwest corner of Spain, at Mina Serrabal, a quartz mine near the city of Santiago de Compostela. Quartz—or more technically, silicon dioxide or silica—is the main component of sand. But at Serrabal it can come in huge pieces twice the width of a smartphone. Mine operator Ferroglobe runs an automated system to sort the silica by size. After the pieces are washed and treated, the big ones head to the Atlantic coast for the next step in the journey.
Fact: According to consultant Thunder Said Energy, 350 million tonnes of silica was mined in 2024.
2. Silicon Metal After an hour by truck, the quartz mini-boulders arrive at Sabón, Ferroglobe’s 125,000-square-meter factory in the coastal province of A Coruña. Here the quartz will be mixed with dehydrated wood chips and heated to 1,500 to 2,000 °C in a trio of electric-arc furnaces that use massive electrodes invented at this plant in the 1990s. Inside the furnace, a reaction takes place that rips the oxygen from the silica and sticks it to the carbon from the wood. The result is silicon metal and carbon monoxide.
Fact: 3.8 million tonnes of silicon metal was produced in 2023, according to the U.S. Geological Survey.
3. Purified Polysilicon The resulting silicon metal is about 98 percent pure, and that’s not good enough. It will need to be at least 99.9999999 percent pure to become a microprocessor, which will require some pretty powerful chemistry. So it’s off to Wacker Chemie, in Burghausen, Germany. Here, the metal undergoes what’s called the Siemens process: It’s bathed in hydrochloric acid and reacts to form hydrogen gas and a liquid called trichlorosilane. Any impurities will be in the liquid, which is then run through a multistep distillation process that separates the pure trichlorosilane from anything unwanted. Once the needed purity is reached, the reaction is reversed: At 1,150 °C, the trichlorosilane is reacted with hydrogen to deposit multiple crystals of silicon, called polysilicon, and the resulting hydrochloric acid gas is sucked away. The polysilicon forms thick rods around heating elements. Once it’s cooled and removed from the reaction chamber, the polysilicon is smashed up for shipping.
Fact: According to consultant Thunder Said Energy, 1.7 million tonnes of polysilicon was produced in 2024, most of that for solar-cell production.
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